1. Field of the Invention
The invention relates to methods and systems for enhancing the detection sensitivity of piezoelectric microcantilevers. The method of the present invention may be particularly beneficial for biodefense, food safety, pathogen detection and diagnostic applications involving body fluids such as serum, saliva, and urine.
2. Description of the Related Technology
Piezoelectric sensor technologies, specifically piezoelectric cantilever sensors, are useful for detecting the presence and/or mass of various compounds and molecules. Typically millimeter-sized, these cantilever sensors are fabricated by bonding a thick layer of a piezoelectric material, such as commercial lead zirconate titanate (PZT), to a non-piezoelectric substrate, such as stainless steel, titanium or glass, and have a number of advantageous properties, such as the capability of electrical self-excitation and self-sensing. Furthermore, piezoelectric cantilevers that include an insulation layer are capable of preventing conduction in liquid media, rendering them promising for biological in-situ electrical detection. Current piezoelectric cantilever sensors, however, generally lack the desired detection sensitivity necessary for many applications, particularly in-situ biosensing applications. These sensors typically have poor piezoelectric properties, characterized by a low −d31 piezoelectric coefficient of less than 20 pm/v.
The detection sensitivity of piezoelectric cantilever sensors, which may be viewed as simple harmonic oscillators, is correlated to the resonance frequency shift capability of the sensor. The resonance frequency shift capability in turn is dependent upon the ability to detect changes in the effective spring constant and effective mass of the sensor. Current cantilever sensor technologies, such as non-piezoelectric microcantilevers and piezoelectric microcantilevers constructed from bulk PZT of relatively large thickness are only useful for methods which detect changes in mass and/or minor changes in the effective spring constant of the sensor.
Enhancement of detection sensitivity, accuracy and efficiency of piezoelectric cantilever sensors would be useful to the development of numerous industries and technological fields, such as bioterrorism defense, health sciences and diagnostic devices. Therefore, there is a need to develop a piezoelectric microcantilever sensor capable of achieving very high detection sensitivities.